Good pics
@Limpinhitter for discussion. I think we all can assume this is a maxish full FH ... no warm up exceptions.
pic 1
About to start uncoiling ... hips past feet ... shoulders past hips
pic 2
uncoiling around back leg (right) hip. Note the hips and shoulders have rotated together ... shoulder line still past hip line
pic 3
between pic 2 and 3, shoulders caught up with hips. Note: this is before contact. From pic 2 to 3, hip and shoulder and hand are traveling together (shoulder and hand in line, hip line forward of shoulder line but rotating together)
pic 4
arm has passed shoulder line. Happens as shoulder reaches an end of range extension point and passes the momentum to the arm.
pic 5 and 6
follow through rotation continues
After watching more video, and shadow swinging ... I have updated my open FH body parts sequence theory.

What remains is:
1) don't believe hips are rotated before shoulders are rotated
2) do believe leg drive and hip rotation happens first, but shoulder and arm comes along at same time
3) by pic 3 above, a lot of arm effort has been added
Something like this:
1) at same time the leg/hip drive happens, we fire the core/shoulder/? muscles required to turn shoulders. No arm effort here yet other than supporting arm and racquet, arm simply travels with shoulder turn. I do not view this as a sequence of hip to shoulder events ... I think it's hip firing and shoulder firing at the same time.
2) between pic 2 and 3, a lot

of arm effort is added (probably at point pulling forward from slot). Most of us agree we add non-dom arm effort in the forward 2hbh swing. I think the same happens with the FH. I thought the significant arm effort happened right when forward shoulder turn started, but have changed my mind. With fh shadow swings, the arm is merely along for the ride at the start of shoulder turn. But long before contact, the arm fires and adds to the rhs. You can see this with fed as he extends his arm ... his hand reaches the full extension point, and then arm effort fires with shoulder turn.
I don't think it's hip/shoulder timing that makes the world class FH. I think it's the timing of the shoulder + arm effort with the magic that happens around the wrist. It's why pros can still hit awesome shots with no hip turn at all ... the timing of the arm at the shoulder and racquet rotation around the hand are constants.
Yes ... Sinjin said I was the kinetic chain flat earther. I prefer to think I was that first guy that said "I don't believe you can get syphilis from a toilet lid".
Disclaimer: The views and opinions expressed in this post are those of BBP and do not necessarily reflect the official policy or position of professional tennis instructors.
Edit: Watched Osteopenia vs Stephens final ... no delay from shoulder turn and arm effort. When they hammer with the shoulder they also hammer with the arm.
ATP FH - arm effort delay after start of shoulder turn. No delay for WTA with arm/hand behind body on backswing.